Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$157.48	9.719%	$172.7855	$172.79	$172.80	$172.80
Purchase #2	$88.78	10.186%	$97.8231	$97.82	$97.80	$97.80
Purchase #3	$242.82	4.595%	$253.9776	$253.98	$254.00	$254.00
Purchase #4	$53.46	11.262%	$59.4807	$59.48	$59.50	$59.50
Purchase #5	$206.97	4.701%	$216.6997	$216.70	$216.70	$216.70
Purchase #6	$73.46	12.605%	$82.7196	$82.72	$82.70	$82.70
Purchase #7	$29.76	4.176%	$31.0028	$31.00	$31.00	$31.00
7 purchase totals =	$852.73		$914.4890	$914.49	$914.50	$914.50